Piezoelectric/electrostrictive device and method of fabricating the same

Abstract

A piezoelectric / electrostrictive device includes a functional element. The functional element includes a base portion; a deformable portion assuming the form of a thin plate and extending from the base portion to thereby form a plane; a piezoelectric / electrostrictive element formed on the deformable portion; and a reflective portion extending from the deformable portion so as to form an active plane intersecting with the plane of the deformable portion, and having a light-reflecting member disposed on the active plane. Operation of the piezoelectric / electrostrictive element causes the deformable portion to be deformed in a direction substantially perpendicular to the plane of the deformable portion to thereby change a reflection angle of light reflected from the reflective portion.

Description

[0001] 1. Field of the Invention[0002] The present invention relates to a piezoelectric / electrostrictive device having a light modulation mechanism for use in an image display unit, an image printing unit, an exposure unit, an optical switch, or a like apparatus.[0003] 2. Description of the Related Art[0004] Recently, various devices having light modulation mechanisms have been developed. For example, Japanese Patent Application Laid-Open (kokai) No. 5-196880 discloses a deformable mirror device (hereinafter called a DMD). As shown in the schematic perspective view of FIG. 33, the DMD includes a CMOS substrate 200; two support elements 202 disposed on the substrate 200; a pair of torsion hinges 204 supported by the support elements 202; a yoke 206 supported by the support elements 202 via the torsion hinges 204; and a mirror 208 supported by the yoke 206. The torsion hinges 204 are twisted through utilization of electrostatic attraction, to thereby change the angle of the mirror 208...

AI Technical Summary

Benefits of technology

[0010] In order to change the reflection angle of light reflected from the light-reflecting member disposed on the reflective portion, the piezoelectric / electrostrictive element causes the thin deformable portion to be deformed in a direction substantially perpendicular to the plane of the deformable portion. Thus, no torsion is exerted on the deformable portion, which serves as a drive portion. Therefore, the deformable portion is unlikely to deteriorate with time. Also, since the active plane of the reflective portion on which the light-reflecting member is disposed is arranged in such a manner as to intersect with the plane of the deformable portion, even when the length of the deformable portion is increased in order to increase the deflection angle (the angle of tilt of reflective surface), there is no need to increase the length of the light-reflecting member in association with the increase in the length of the deformable portion. Accordingly, the above-described configuration enables provision of a piezoelectric / electrostrictive device of small size and high reliability, thereby enabling highly dense arrangement of pixels in application to, for example, an image display unit. Notably, the degree of reduction in the size of the piezoelectric / electrostrictive device becomes greatest when the active plane of the reflective portion and the plane of the deformable portion intersect at right angles.

[0039] As mentioned above, after the plurality of unitary bodies are bonded at the thick (thick wall-like) portions while the spacers are interposed therebetween, and before the light-reflecting member is formed, a filler is filled into gaps between the plurality of unitary bodies, followed by polishing the surface on which the light-reflecting member is to be formed. Subsequently, the light-reflecting member is formed on the polished surface. Then, at least the light-reflecting member and the residual thick (thick wall-like) portion are cut. Finally, the filler is removed. Since the filler is present between the plurality of unitary bodies during polishing and cutting in the second cutting step, polishing and cutting can be stably performed.

Problems solved by technology

Also, since the light-reflecting member 318 is formed of a thin metal film, whose rigidity is low, the reflective surface implemented by the light-reflecting member 318 encounters difficulty in maintaining flatness.

Since the flatness of the reflective surface changes with time as a result of operation of the AMA, the operation of deflecting the reflective surface cannot be performed stably over a long period of time.

Therefore, the deformable portion is unlikely to deteriorate with time.

Thus, the AMA encounters difficulty in maintaining good flatness of the reflective surface over a long period of time.

However, such a dimensional relationship is not the only means for preventing deformation of the reflective portion 13.

Such materials are likely to react with a piezoelectric / electrostrictive material during heat treatment of a piezoelectric / electrostrictive layer, causing the material composition to vary with a resultant deterioration in piezoelectric characteristics.

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